1. Field of the Invention
The present invention relates to a Ni—Cu—Zn based ferrite material, in particular, a Ni—Cu—Zn based ferrite material which has a permeability stable against the temperature variation in the use environment.
2. Description of the Related Art
Ni—Cu—Zn based ferrite materials are widely used, for example, as cores for inductors and transformers, and as cores to remove noises for portable appliances such as cellular phones and notebook-size personal computers. Portable appliances are used in various environments because of the portability thereof. Accordingly, the components constituting a portable appliance are required to be highly resistant to environmental variations, and particularly important is the resistance thereof to temperature variation. This is because temperature is varied depending on the season and additionally varied largely depending on the site where the appliance is used. As for the Ni—Cu—Zn based ferrite materials, it is important that the permeability is stable against the temperature variation.
Various proposals have hitherto been presented for Ni—Cu—Zn based ferrite materials.
For example, Japanese Patent No. 3147496 (Patent Document 1) discloses, as a ferrite material which is scarcely affected by the stress such as contraction force of the resin in molding with resin and suitable for applying to laminated ferrite parts and formed (molded) ferrite parts, a ferrite material comprising Fe2O3: 46.5 to 49.5 mol %, CuO: 5.0 to 12.0 mol %, ZnO: 2.0 to 30.0 mol %, NiO: the balance, wherein the ferrite material is further blended with Co3O4, Bi2O3, SiO2 and SnO2 in contents of Co3O4: 0.05 to 0.60 wt % and Bi2O3: 0.50 to 2.00 wt %, and in a combined content of SiO2 and SnO2: 0.10 to 2.00 wt % (exclusive of the case where either SiO2 or SnO2 is 0 wt %) in relation to the Ni—Zn—Cu based ferrite material.
Additionally, Japanese Patent Laid-Open No. 9-306716 (Patent Document 2) discloses a ferrite sintered body which is high in saturation magnetic flux density and small in the temperature coefficient of the initial permeability, wherein the sintered body comprises as main constituents Fe2O3, NiO, ZnO and CuO, and is added with at least one of PbO and H3BO3 in a content of 0.00211 to 0.00528 mol % or Bi2O3 in a content of 0.00101 to 0.00253 mol %, and at least one of SiO2, Cr2O3, Al2O3, SnO2 and WO3 in a content of 0.00392 to 0.00982 mol %, when the sum of the contents of the main constituents is represented as 100 mol %.
Moreover, Japanese Patent Laid-Open No. 2001-6916 (Patent Document 3) discloses a low-loss oxide magnetic material as a low-loss oxide magnetic material having attained a low power loss, wherein the material comprises as main constituents 43 to 50 mol % of Fe2O3, 10 to 40 mol % of NiO, 1 to 15 mol % of CuO and ZnO constituting the balance, and comprises as additive(s) 0.005 to 0.1 wt % of at least one of CaO, Cr2O3, MgO, Al2O3 and P2O5.    [Patent Document 1] Japanese Patent No. 3147496    [Patent Document 2] Japanese Patent Laid-Open No. 9-306716    [Patent Document 3] Japanese Patent Laid-Open No. 2001-6916